Energy Function Analysis For Power System Transient Stability

The destruction of power stability is the most serious accident in grid. Along with dimensions are gradually augmented, in order to prevent this accident, the issue of transient stability of power system is more and more important subject. There are two main methods for transient stability analysis. One is so-called time-dominated simulation method, which has higher calculating precision and can deal with the complex system model, but can't give stability margin and its calculation speed is too slow, so it only is an off-line method. Anther is so called direct method. Hereinto, energy function method is the one crucial direct method. Its advantages lay in that it can give stability margin and has fast calculation speed.In recent years, Energy Function Method Analysis for fast Power System Transient Stability has attracted many researchers. They have made much research on it to rise the calculating precision, and the precision basically satisfies the demand of power system on-line dynamic safety analysis. The method can be used as instrument for transient stability on -line scan analysis.The main contents in the thesis are as follows:Firstly, the development and application of direct method are summarized. Basic stability theory and its application in transient analysis are introduced. Making use of an single machine-infinite system, this thesis analyses the whole process of transient stable analysis by using direct method;Also gives the definition of transient energy function and itscalculation, and how to fixes the critical energy and the standardized margin degree of stability. The thesis compares the direct method with equal-area criterion and finds out the conclusion of their uniformity.Secondly, Aiming at classical mathematics model of Multi-machine System, state equation and transient energy function are putted forward in the center of angle. The theory bases of PEBS/BCU method are analyzed. Based on the above bases, the transient stability analysis process of PEBS/BCU methods are summarized, and the two methods are analyzed. Because energy function method is based on differential equation model, adopting contractive system equation of generator are rigid, the characters of rigid equation are detailedly researched in this paper. Furthermore, automatic switching orders and steps equation is adopted to solve the integral problem of contractive system trajectory, and the calculation example is given.Thirdly, a PEBS/BCU program for power system dynamic security is provided. The critical energy and energy margin is quickly evaluated by TEF-BCU method in order to decide whether or not the system will be able to maintain its synchronism. And the transient stability of six-machines system with twenty-two nodes are analyzed in this program, the transient stability analysis calculation results of six-machines system are given. And transient stability analysis is discussed. At the same time, the ameliorative suggestion is put forward.